1. Field of the Invention
The present invention generally relates to a mobile communication system, and more particularly to a method and system for monitoring the traffic carrier performance of a CDMA carrier.
2. Description of the Related Art
Drive team testing is a labor intensive process that is expensive, time consuming, and often incomplete. Drive team testing requires dispatching a mobile unit into a selected zone of coverage to make a first hand observation of system conditions. The current drive team testing methods include: Mobile Diagnostic Monitor (MDM), Mobile Station Test (MOST), and Test Carrier. Each method includes drawbacks associated with monitoring the performance of a traffic carrier during a test drive.
MDM is a software tool for collecting drive-test data with a mobile phone. The mobile station follows the standard call processing procedures. For a CDMA multi-carrier system, when a mobile station originates or receives a call, the cellular system assigns a traffic carrier on one of the equipped carriers of the sector. The assignment is based on that sector""s own assignment algorithm. The traffic carrier assigned to the mobile unit can be different depending upon the prevailing system conditions (i.e., RF loading, system resources, etc.). It becomes inconvenient to monitor the performance (i.e., call drop rate, handoff completion rate, lost call, etc.) of a particular traffic carrier during a test drive as a consequence of assigning different traffic carriers to the mobile station. The method is deficient to the extent that, as a consequence of assigning different traffic carriers, there is no guarantee that all the desired performance data will be collected for the desired carrier.
In the Test Carrier method, the test mobile directs xe2x80x9ctestxe2x80x9d mobile stations (e.g., those assigned Access Overload Class =10) to make initial system access using the carrier under test, and the normal subscriber (i.e., non-test) mobiles to make initial system access using either a carrier already in service, or any carrier assigned to the sector. This feature minimizes service provider fears about the impact of testing upon their subscriber base, by restricting subscriber mobile stations to non-test carriers, while providing full system access to test mobiles.
This feature requires the service provider to assign a test carrier to each cell on the drive test route requiring an excessively large data assignment. This occurs because each sector can have only a single carrier assigned as a test carrier. It is not practical for a technician to use different handsets to monitor the traffic carrier performance on the different carriers.
In the Mobile Station Test (MOST), technicians are permitted to use a mobile unit as a test station (i.e., a MOST mobile unit). When used as a test station, the MOST mobile unit enables the technician to test a cell-to-mobile unit call processing interface and to check the audio quality on all the carrier elements on a cell by entering the forced handoff function code to have call handoff from one carrier element to another carrier element on the cell. When monitoring the traffic performance of a specific carrier with the MDM, the technician has to repeatedly enter the forced handoff function code until the call is handed off to a traffic channel of a desired traffic carrier. When the call is dropped during the test drive and only one technician is on the test drive route, it is very inconvenient for the technician to dial a lot of numbers from the mobile station.
Accordingly, a need exists for a method and system which overcomes the disadvantages in the prior art.
The present invention provides a method and system for monitoring the traffic carrier performance of a CDMA carrier. In a first embodiment of the present invention, a desired traffic carrier (DFC) database, specific to the present invention, can be located with and controlled by each base station, base station controller (BSC), or mobile switching center (MSC) in a mobile communication system. Each DFC database includes a record for each service provider""s test mobile station in the communication system. Each DFC database record includes at least two data fields: a mobile station identification field which is the record index, and a preferred traffic carrier field which identifies a preferred traffic carrier which represents the traffic carrier to be preferably selected for assignment to the mobile station involved in a call setup.
As is well known in the art, each base station operates on a subset of the radio frequency (RF) carriers assigned to the system. The preferred traffic carrier represents the RF traffic carrier to be preferably assigned to a mobile station from among the RF carriers assigned to the servicing base station.
In operation, during a call setup for a particular mobile station, where the mobile station either originates or is the recipient of a call, the servicing base station accesses the DFC database specific to the macro-cell, and uses a predefined mobile station identifier as an index into the database to retrieve the record pertaining to the particular mobile station originating/receiving the call. Once the record has been identified, the base station retrieves the preferred traffic carrier from the record, and attempts to assign the preferred traffic carrier, if available, to the mobile station to complete the call setup. If the preferred traffic carrier is available, the call can be setup by one of the following methods:
1. The system assigns the preferred traffic carrier during the call setup. In this case, the initial assigned carrier is the same as the preferred traffic carrier; or
2. The system assigns a carrier following the standard normal call setup procedure. In this case, the initial assigned carrier may be different from the preferred traffic carrier.
If the preferred traffic carrier is not available during the call setup, the method provides for one of the following alternatives:
1. Make a standard traffic carrier assignment during the call setup stage (see item 2 above).
2. Provide the mobile subscriber with a message announcement or predetermined tone indicating the call cannot be setup.
If (1) is selected, a counter will be initiated during which a continual check will be made to determine whether the preferred channel has become available. In the event the initial assigned carrier is different from the preferred traffic carrier, upon completion of a successful call setup (i.e, traffic channel acquiring procedure completes successfully), the system directs the mobile to hand off the call to the preferred traffic carrier.
Advantageously, a technician only needs to bring a single test mobile for system monitoring, that has preferred traffic carrier assigned to it. With this feature, a technician need not bring multiple handsets and make multiple call attempts to ensure that the test call is assigned on the carrier that will be monitored.
Another advantage of the present invention is that if a call is dropped or lost while being monitored during a drive test, a technician is only required to re-establish the call without being concerned about assigning a particular traffic carrier. In the event a call is dropped or lost, an attempt is made to preferably re-establish the call on the preferred traffic carrier, thereby allowing for complete and expedient testing of a coverage area than was previously possible via standard testing schemes.
A further advantage of the present invention is that the DFC database allows for effortless software upgradability and expansion of the testing system.